5.2.5 - Light independent Reactions

Question 1

What prodcuts from light dependent reactions are used in light independent reactions?

Answer 1

ATP and NADPH

Question 2

Where do light independent reactions occur?

Answer 2

Stroma

Question 3

What happens first in the Calvin cycle?

Answer 3

Carbon dioxide diffuses into the stroma.
The enzyme rubisco has a binding site for carbon dioxide and ribuose bisphosphate theses to compounds combine

Question 4

What happens early on in the Calvin cycle when carbon dioxide reacts with ribulose bisposhphate?

Answer 4

An unstable 6 carbon compound is formed.
This then breaks down to form 2 molecules of glycerate-3-phosphate.

Question 5

What happens to glycerate-3-phosphate when it is formed in the Calvin cycle?

Answer 5

It’s reduced by NADPH which requires ATP.
This forms 2 molecules of Triose phopshate

Question 6

What happens to 5 out of every 6 triose phosphates?

Answer 6

They are recycled to make 3 molecules of ribulose bisphosphate.
This process requires phosphorylation of ATP

Question 7

What happens to some of the molecules of Glycerate-3-phosphate?

Answer 7

Converted into amino acids and fatty acids.

Question 8

What can triose phosphate be used for other than being recycled into ribulose bisphosphate?

Answer 8

Can be used to build monosaccharides such as glucose.
Can be converted to glycerol which joins with fatty acids to form lipids.

Question 9

Give a summary of what the light independent stage does.

Answer 9

The light-independent stage is where carbon dioxide is fixed and used to build complex organic molecules.

Question 10

Why is there only a small amount of RuBP in the stroma of the chloroplasts?

Answer 10

Continually being used in the fixation of CO2

Question 11

Explain why a lack of nitrates in the soil can lead to a reduction in growth of plants.

Answer 11

Less nitrates means fewer amino acids and therefore proteins. Fewer enzymes such as Rubisco rate affected.